You have to specify the time for each frame using ImageDelayTime[] property. Example:
var
i:integer;
begin
// set time for each frame
for i:=0 to ImageEnMView1.ImageCount-1 do
ImageEnMView1.ImageDelayTime[i] := 100; // 100 milliseconds
// now play
ImageEnMView1.Playing := SpeedButton1.Down;
end;